In recent years, technologies for producing a gasified gas by gasifying a gasification raw material such as coal and fuels that were not used before, including biomass, tire chips, and the like, instead of petroleum have been developed. Such a gasified gas produced in that manner is being used in power generation systems, production of hydrogen, production of synthetic fuels (synthetic petroleum), and production of chemical products such as chemical fertilizer (urea). Among gasification raw materials which serve as raw materials of a gasified gas, coal in particular can be mined for the next 150 years, which is three times longer than petroleum, and deposit areas thereof are more evenly distributed than those of petroleum, and thus it is expected as one of the natural resources that can be stably supplied for a long period of time.
In the past, a gasification process of coal was performed through partial oxidation using oxygen or air, but due to the necessity of partial oxidation at a high temperature of 2000° C., the process has a drawback of increasing costs of a gasification furnace.
In order to overcome this problem, a technology for gasifying coal at a temperature of about 700° C. to 900° C. using water vapor (water vapor gasification) has been developed. In this technology, costs can be reduced by setting a low temperature. However, a gasified gas produced thus often includes a larger amount of tar than a gasified gas produced through partial oxidation at the high temperature of 2000° C. When the temperature of a gasified gas is lowered in the process in which the gasified gas produced through the water vapor gasification is used, tar included in the gasified gas condenses, which causes a problem of clogging of a pipe, breakdown of a device used in the process, poisoning of a catalyst, or the like.
Thus, a technology for removing tar included in a gasified gas by combusting the produced gasified gas with oxygen or air to raise its temperature to 1100° C. or higher thereby causing tar to undergo oxidation reforming has been disclosed (for example, Patent Document 1).